The present invention relates generally to tube couplings, and more particularly to tube couplings of the type that are known as quick connect tube couplings.
Quick connect tube couplings permit a tube to be sealingly connected to a body by straight line axial movement of the tube and without any tools. Such quick connect tube couplings are used in a wide variety of applications that require the tube coupling to be dependable and easy to use.
Quick connect tube couplings may include an annular elastomeric seal for preventing fluid leakage and a snap ring for securing the tube in place after assembly. The seal of such tube couplings is generally considered a dynamic seal, because the tube is usually able to move axially a small amount relative to the body after assembly due to manufacturing tolerances.
In U.S. patent application Ser. No. 754,567 filed Dec. 27, 1976, and now U.S. Pat. No. 4,133,564 and in U.S. Pat. Nos. 2,521,127, 3,847,421 and 2,935,343, quick connect tube couplings are disclosed in which the snap ring and the seal may be preassembled on the tube before inserting the tube into the body. In U.S. patent application Ser. No. 735,949 filed Oct. 29, 1976, and now U.S. Pat. No. 4,063,760 a quick connect tube coupling is disclosed in which the seal and the snap ring are preassembled on the body before the tube is pushed into the body.
The present invention provides a quick connect tube coupling which has a large seal surface area to prevent leakage and which can be assembled with a low axial force. This is a result of an arrangement according to the present invention which provides a large seal but does not require full compression of the seal during assembly.
An additional feature of the invention is the provision of a subassembly having a nut, a snap ring, a seal, and a retainer which secures the snap ring and the seal in place during assembly. The retainer also provides a back stop for the seal and captures the snap ring after assembly to prevent the tube from being pulled out of the body.
Both of the above described features are accomplished according to the principles of the invention by an arrangement which is relatively simple and easy to manufacture and which requires a relatively small amount of working of the tube. According to the principles of the invention, the body includes a fluid flow passage which has a nominal diameter portion, a counterbore portion, and a threaded end portion. A nut which carries the seal and the snap ring is threaded into the threaded end of the fluid flow passage in the body. The nut includes a tube receiving passage which has a counterbore near one end for receiving the snap ring.
A retainer is provided near one end of the nut for holding the snap ring in the counterbore and for properly positioning the seal relative to the nut. The retainer includes an axially extending cylindrical portion which is frictionally received in the passage in the nut. A radially inwardly extending tab portion of the retainer extends along one side of the snap ring to hold the snap ring in its counterbore. The seal is frictionally retained in the cylindrical portion of the retainer, and the radially inwardly extending tab portion of the retainer positions the seal relative to the retainer. A radially outwardly extending tab portion of the retainer positions the retainer relative to the nut so that the seal is accurately positioned relative to the nut and so that the retainer is positively locked in place upon assembly.
When the nut and the portions which are carried by the nut prior to assembly are assembled in the fluid flow passage in the body, the radially outwardly extending tab of the retainer is squeezed between the radial end face of the nut and a shoulder in the body passage so that the retainer can not move. This locks the retainer in place after assembly so that the retainer can lock both the snap ring and the seal in place after assembly of the tube.
The tube which is used in the coupling according to the present invention has a reduced diameter end portion, an annular groove, and a conical ramp therebetween. As the tube is pushed into the passage, the snap ring is expanded radially outwardly by the conical ramp. The reduced diameter end portion of the tube is received within the seal. When the conical ramp engages the seal and the tube is pushed further into the body, the conical ramp carries the seal with it to a forward position in the body counterbore. By this arrangement, the very large seal which is used in the coupling according to the present invention is not fully expanded radially outwardly and is not fully compressed between the tube and the body during axial insertion of the tube. This significantly limits the axial force required to assemble the tube. When the tube is pushed into the body the proper amount, the snap ring snaps into the annular groove in the tube to prevent the tube from being pulled out of the body. When the fluid flow passage in the body is subjected to fluid pressure, the fluid pressure acts on the seal and pushes the seal radially outwardly along the conical tube ramp and axially rearwardly to a radially confined position against the retainer.